Conventional liquid crystal display devices of this type have a transmissive liquid crystal panel, and a backlight is used in the back of the transmissive liquid crystal panel. For the light source apparatus used as a backlight, CCFL (Cold Cathode Fluorescent Lamp) has conventionally been a main stream. However, with recent progress in LED technology, use of the LED as a light source is regarded as promising instead of using the CCFL.
In a direct LED backlight of Patent Document 1, a method is used for controlling streaked and uneven brightness due to the overlapping of shadows created by pillars and adhesive resin of optical lenses blocking light from a light emitting element. However, optical diffusing lenses used therein are all the same.
FIG. 11 is a longitudinal cross sectional view showing a configuration example of an essential part of a conventional light emitting module, on which a light emitting element disclosed in Patent document 1 is mounted. FIG. 12 is a plane view showing an arrangement example of optical lenses in a plane emitting unit on which a plurality of light emitting element modules of FIG. 11 are mounted.
As shown in FIG. 11, in a light emitting element module 100, a plurality of light emitting element parts 102 are mounted on a substrate 101 as light emitting elements, the light emitting element parts 102 being equipped with LEDs and the light emitting element parts 102 being arranged either in one column or in a plurality of columns.
In the substrate 101, wiring is provided on a base material 101a formed by impregnating, for example, a resin (epoxy resin, cyanate resin and the like) into woven or non-woven, glass fiber, organic fiber or the like. White insulation material (white resist and the like) 101b is formed on the uppermost surface of the substrate 101 in such a manner to cover a region except for a land part in the wiring. Covering the uppermost surface of the substrate 101 with the white insulation material 101b increases reflection rate of light from the light emission elements and increases light irradiation amount to a display area, in addition to protecting the wiring. Note that ordinary solder resist can be used if a reflection sheet is provided separately on the surface of the substrate.
In a light emitting element part 102, one or a plurality of LED chips (not shown) are mounted on a part substrate 102a such as ceramic, and the LED chips are electrically connected to the part substrate 102a with wires (not shown). Thus, the LED chips and wires are formed by being sealed by a sealing resin 102b. For the seal resin 102b, transparent resin such as silicon is used, and fluorescent materials are added as needs arise.
The substrate 101 has an opening 101d which is not covered with the insulating materials 101b. In the opening 101d, an optical lens 103 and the base material 101a of the substrate 101 are fixed with adhesive resin 104.
The size of the opening 101d is the same as, or slightly greater than, that of a bottom surface of a pillar 103a of the optical lens 103. As such, providing the opening 101d the size of which is the same as or slightly greater than the size of the bottom surface of the pillar 103a facilitates the positioning of the adhesive resin 104, thus facilitating the control of resin amount. If the amount of the adhesive resin 104 is too much, then the adhesive resin 104 will rise up to the bottom surface of the lens section 103b of the optical lens 103, or will spread to the surface of substrate 101 beyond the opening 101d. As a result, transmitted light may be blocked or absorbed at the bottom surface of the lens section 103b or the pillar 103a, which may influence the diffusion of light from the light emitting element.
At the center of the optical lens 103, a recess 103c is formed for partially housing the light emitting element part 102 from the bottom. The light emitting element part 102 is not sealed and has a layer of air between the light emitting element part 102 and the recess 103C, which provides favorable heat radiation of the light emitting element part 102.
In addition, in a conventional plane light emission unit 110 as shown in FIG. 12, pillars 103a of each of optical lenses 103 and adhesive resins 104 adjacent to each other are arranged to commonly prevent a straight line L1 in a longitudinal direction and a straight line L2 in a transverse direction, where the lines connect the centers of the light emitting element parts 102 adjacent to each other. As a result, shadows created by pillars 103a of the optical lenses 103 and adhesive resins 104 blocking light from a light emitting element will not overlap with each other, thereby controlling the occurrence of streaked and uneven brightness.